The Tragedy Surrounding The Birth of Tragedy
You wouldn't know it by looking at most professors, but academia is a total bloodsport. Say one thing that goes against mainstream scholarly opinion, and your academic career goes "poof" (good thing we've got tenure to fall back on). As it turns out, Nietzsche said quite a few things that went against mainstream scholarly opinion in his first book The Birth of Tragedy, and his critics never let him forget it.
For one, philology was supposed to be an empirical field, meaning that philologists had to thoroughly reference their works and use evidence to back up their points. The Birth of Tragedy, on the other hand, was highly speculative, and it sometimes seemed like it was more about Richard Wagner than it was about Greek tragedy. It was.
The top philologists of the day had very few good things to say about the book, and even Nietzsche's biggest fan—his mentor Friedrich Ritschl—was privately disappointed with his pupil's deviant scholarship. The worst critic of all turned out to be Nietzsche himself, though, who later went on to all but totally denounce The Birth of Tragedy with his trademark acidic wit.
Yet in spite of the fact that the author himself dissed it, The Birth of Tragedy is still considered a super important work of philosophy. Go figure.